1. Field of the Invention
This invention relates to electronic computation circuits, and more particularly to a multifunction arithmetic logic circuit having comparison and numeric conversion circuitry.
2. Background Information
In many high speed electronic systems, such as graphic processing systems, a large number of mathematical calculations must be performed. For high speed electronic systems, time is of the essence in performing such calculations. Therefore, it is desirable to have a dedicated circuit that can perform such mathematical functions at a very high rate of speed. In the graphics area, it is particularly desirable to have such a circuit that can perform calculations on floating point numbers, fixed point numbers, and logical data. It is also desirable to be able to convert floating point numbers to fixed point numbers, and vice versa. It is further desirable to be able to compare the values of two numbers, and to be able to track changes in the value of a string of such comparisons for purposes of determining whether an object in a graphics environment is to be displayed. In the prior art, some of these functions have been performed by a dedicated integrated circuit. A typical circuit is the Weitek Corporation WTL 1033 Arithmetic Logic Unit. However, the known prior art integrated logic circuits are not optimized for use in a graphics processing system, and do not include many desirable functions.
Therefore, it is an object of the present invention to provide a high speed pipelined architecture arithmetic logic circuit having a number conversion subcircuit, a number comparison subcircuit, and a visibility logic subcircuit particularly useful in a graphics processor. The invention is described in the context of an integrated circuit capable of performing such calculations in 300 nanoseconds, with a throughput rate of 100 nanoseconds at a clock frequency of 10 MHz.